Diagnostic instrument



FIG. 1 is a perspective view of the diagnostic instrument with a finger receptor in the open position;

FIG. 2 is a perspective view of the diagnostic instrument with the finger receptor in the closed position;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a left side elevational view thereof;

FIG. 7 is a top plan view thereof; and,

FIG. 8 is a bottom plan view thereof.

Environmental elements of the disclosure shown in broken lines form no part of the claimed design. 

The ornamental design for a diagnostic instrument, as shown and described. 